How to create NuGet package that only add JavaScript/CSS files to web-based project?

I have some NuGet package that contains both DLL file and web related files like JavaScript, Stylesheet and image files. I want to create package that only install web related file to web project only (including ASP.NET and ASP.NET MVC project). What is
the easiest way to do that?

You can create two packages. The first package will contain the dll file. The second package will contains JS/CSS files and depend on the first one. The general convention is to append '.Web' to the first package's Id to name the second package.